In order to avoid loss of life at sea, the International Maritime Organisation (IMO) has placed significant attention towards the requirement for all ships at sea to carry lifesaving equipment and to maintain such equipment in an order suitable for use in the event of an incident that requires personnel to abandon the ship.
For many passenger ships, there is a requirement to carry lifeboats which can be used to carry passengers and crew which can be deployed from the ship in an emergency to evacuate the passengers and crew from immediate danger. The lifeboat may take a variety of forms and may be self-propelled and have provisions contained therein which provide a degree of control to the passengers of the lifeboat and the ability to survive until they are rescued by a rescue craft or the like.
In the Marine Oil and Gas industry, there is a requirement to employ highly skilled diving contractors to spend large periods of time underwater at significant depths to perform a variety of tasks, such as the maintenance and repair of subsea infrastructure. Due to the extreme depths at which the divers are required to operate and the duration at which they are required to remain underwater, the divers are maintained at a desired pressure for the duration of their time at work, this aids in avoiding health risks associated with undergoing multiple decompression processes, and the time associated therewith. Such a phenomena is known as saturation diving.
In instances where saturation diving is employed, a dive support vessel stationed at sea is equipped with a hyperbaric environment on the water surface to which the divers can retreat to rest and sleep when they are not working underwater. The hyperbaric environment generally comprises a set of linked pressure chambers made up of living chambers and transfer chambers that allow the divers to retreat to a living chamber when not working underwater, without having to undergo decompression after each dive. As it is not uncommon for the divers to work on a project for several days or weeks, the divers only require decompression to surface pressure at the end of their work, which can be done at a conservative rate to reduce the potential for decompression illness.
It will be appreciated that in such a saturation environment, any exposure of the individual to surface atmospheric pressure will quickly result in the individual becoming severely sick, with death being a real possibility. As such, in the event of a problem associated with the dive support vessel or the saturation system whilst at sea, such as a fire or the like that requires an emergency evacuation, care needs to be taken to ensure that the divers are able to be evacuated and maintained at the appropriate pressure consistent with their previous environment.
For this purpose hyperbaric lifeboats and hyperbaric rescue capsules have been developed to provide a means for divers to evacuate from the environment whilst being maintained at the desired pressure. A hyperbaric lifeboat is typically manned by a coxswain and crew who are at surface pressure and can sail the lifeboat to an appropriate decompression facility or rescue vessel. Within the lifeboat, the divers are contained within a compartment that is maintained at saturation pressure such that they are not exposed to surface pressure. Similarly, a hyperbaric rescue capsule provides one or more hyperbaric chambers for accommodating one or more divers, but the capsule is not manned by a coxswain and/or crew.
At present, hyperbaric lifeboats and rescue capsules are capable of maintaining a pressurised environment for a minimum period of 72 hours. Within this period the lifeboat or rescue capsule, is to be retrieved from the water and transported to a Hyperbaric Reception Facility to undergo a controlled decompression routine to return the divers to atmospheric pressure. Failure to retrieve the divers in this time period may result in the death of the divers.
Thus, it is important that if a hyperbaric lifeboat or rescue capsule has been deployed it is collected and returned to a hyperbaric reception facility as quickly as possible. For this purpose, many vessels are fitted with cranes to facilitate lifting of the lifeboat or capsule from the water for transportation.
One such crane or lifting system that has been proposed for this purpose is disclosed in Australian Innovation Patent No. 2012100144, the entire contents of which are incorporated herein by reference. This patent discloses an A-frame type lifting device that is fitted to the stern of the recovery vessel and which is able to be raised and lowered to extend beyond the stern of the recovery vessel to lift and return the lifeboat to a cradle located between the stern of the vessel and the A-Frame.
Whilst such a lifting system as that disclosed in Australian Innovation Patent No. 2012100144 may be effective in recovering lifeboats or capsules in a timely and efficient manner, if there is a heavy sea, the means for engaging with the lifeboat or capsule, can be dangerous and time consuming. As a hook may weigh in the vicinity of 485 kg and the sling assembly that is attached to the lifeboat may weigh in the vicinity of 120 kg, such devices may be difficult to connect, even in calm seas. Further, in the event of a rough sea, any contact between an individual or the lifeboat/capsule and the devices can be dangerous. Hence, whilst the lifting device may be effective in lifting the lifeboat/capsule from the water for transport, considerable time can be wasted in actually hooking the lifeboat/capsule to the hoist system and/or in heavy seas it may simply not be possible to actually hook the lifeboat/capsule onto the hoist system, significantly delaying the critical recovery.
Thus, there is a need to provide a system and method for retrieving a vessel from water that is quick to capture and engage the vessel and which reduces or substantially ameliorates the likelihood of injury to all associated personnel during the attachment process.
The above references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art. In particular, the above prior art discussion does not relate to what is commonly or well known by the person skilled in the art, but assists in the understanding of the inventive step of the present invention of which the identification of pertinent prior art proposals is but one part.